Antenna system and method



Sept. 1, 1931. F. A. KOLSTER ET AL ANTENNA SYSTEM AND METHOD 3 Sheets-Sheet 1 Filed Feb. 21, 1928 F ICE-l 'FIE E fFear/ck 4 Ko/sfe geoffrey W5 A TTO Sept. 1, 1931. F. A. KOLSTER ET AL 32K ANTENNA SYSTEM AND METHOD Filed Feb. 21, 1928 3 Sheets-Sheet 3 FIE J J IN VE/V TOR Frederick H. K lafer geoffie @443; MWW"W A TTOR EYS Patented Sept. 1, 1931 UNITED STAT-ES tantra PATENT ()FFICE' FREDERICK A KOLSTER AND GEOFFREY GOTTLIEB' KRUESI, 0F PALO ALTO, CALIFOR- -NIA, ASSIGNORS 'IO' 'F-EDERAL TEBEGRAPH*GOMANY;' OF $31? FORNIA, A CORPORATION" OF CABI-FORNIA ANTENRK sysrnu AND .mirnon Application'ifiled Iebruary 121, .1928. Serial No. 255,888.

This invention relates to directional radio signalingand has as an object the obtainment of compactness and simplicity of Construction in uni-directional antennae.

It has been commonly .known that under proper operating conditions an antenna systerm may be given {directional characteristics by. utilizing two or more antenna conductors spaced apart one half wave length oflthe 0scillatory energy being utilized. 'QOnedifiiculty with systems of this kind isthat they occupy a relatively large area and cannot therefore be constructed as a um'tarystructure. To avoid difliculties in directly supply ing oscillatory energy to. all of theiconductors, antenna systems of this 'kind whenns ed for transmitting signalsliave dependedlargely upon energy absorbed and re.-.radiated:;by reflecting antenna ronductorsspaced a definite distance'from the-conductors which are coupled to the transmitter. Arrangements of this .kind can. only approximate a unidirectional effect, since. the re-radiated energy is never of the sameamplitude aslthe energy radiated directly from the main antenna conductors.

In accordance with our inventionare propose to supply, all of theantenna. conductors of an antenna system-.frointhe same source of energy, and by 'properlyieontrollingthe relative phaseangles-of theantenna currents, we are enabled to position' the 1 antenna conductors within a "relatively--.'small .space.

When utilizing the system-fortransmitting.

relatively short wave lengths, say from between 5 to 100-meters,we are a'bleto supply relatively large currents to a: very compact unitary antenna structure.

' he invention willnow be'explain'ed in detail in connection with the drawings in which:

Figs. 1.2, and 3are circuit diagrams illustrating three. different. modifications. of the invention.

FRANCISCO, CALI- -Figs. 4 and 5 are diagrams, illustrating Fig. 9 1s a diagram illustrating the d1rectionallcharacteristics of a system in accordance 'Wit-hthe invention.

ig. .10; is a circuit diagram illustrating a modification of the systems shown in Figs. 1 to.3. 1 Fig. 11 is a vector diagram illustrating the phase relationship between the currents in diiierent parts of the circuit shown in Fig. 10. Our invention may be outlined briefly as comprising an antenna structure in which the conductors are all supplied with current from a single source, but in which the phase relationships of the currents are so controlled as to secure substantially unidirectional effect. Referring to Fig. 1 for a detailed explanation .of-one embodiment of the invention, we have shown a pair of antenna conductors 11 and 12 which are preferably supplied with oscillatory current from a suitable oscillator. 10. Instead of using two independent conductors we prefer. to form these conductors :11 andl2 as opposed portions of a loop, the upper portion of this loop being formed by conductor 13. For tuning the loop to the desired Wave length we have shown a variable capacitance 14 connected across the loop end. Connected to conductor 13, preferably at a point approximately midway between conductors .11 and 12, there is a third conductor 16 which is likewise associated with the oscillator 13. Associated with the ends of the loop there is also a reactive balancing arrangement which serves as ameans for controlling thecurrentdistribution in the loop and which may conveniently be formed by condenser electrodes 17 between which is disposed the adjustable electrode 18. Electrodes 17 are connected to the loop ends, while the intermediate electrode 18 is preferably connected to some point of neutral potential. Conductor 16 is preferably connected to electrode 18 and thus to a point of neutral potential hru a suitable reactance such as the variable capacitance 19.

A variety of signaling circuits may be associated with the antenna. The diagram shows an oscillation generator comprising an electron relay 21 having its plate circuit tuned by means of an inductance 2 For telegraphic signaling, the generation of oscillations may be controlled by means of a.

key 23 inserted in the curren supply cir cuit for the plate of relay 21. Suitable high frequency chokes 24: are prc'lerably utilized upon both positive and negative terminals of the battery 26 or other source of plate potential. The grid of relay 1 is connected to the filament or cathode thru a suitable leak 27, and one terminal of the inductance is connected to the grid thru a suitable condenser 28. \Ve prefer to provide a loop of such size that the capacitance let may be relatively small for tuning the system to a given wave length, and in practice we have sccured best results by forming a single loop with a length of wire slightly less than one quarter wave length of the oscil atory energy to be utilized. The particular oscillator circuit which we have shown is desirable where the etlective resistance of the loop is relatively low, but where the erieetire resistance is of a higher value, we can obtain good sults by employing an ordinary liNlllQilN) feed back type of oscillator. The operation of the above system may best be understood from an explanation of certain basic principles involved. Retesring to Fig. 4 it will be presumed radiators or antenna conductors A and B are supplied with oscillatory energy from separate oscillators as indicated. It will also be presumed that the oscillators supply on rents of equal amplitude and of the same wave length.

Referring now to Fig. 5, with respect to some point C which remote from an antenna comprising conductors at A and B, the phase relationship of currents produced in an antenna at C by waves radiated from conductors at A and 13 will depend upon the respective times required for energy to travel from points it and B to point C. Assuming for example that it, B. and C are in alinement, then the phase relationships be tween the currents produced at an antenna at C will be determined by the distance (Z between points A and B. p

In order to secure tic correct phase relationship between the currents in conductors A and B to secure neutralization of cnero" in one direction and concentration of energy radiated in the opposite direction, we have discovered and verified the tact that distance (K may be made substantially less than one halt the wave length of the energy transmitted, provided a certain phase displacement is maintained between the currents supplied to conductors A-and B. 'We have found that the correct phase angle for unidirectional transmission may be expressed as equal to i i 21rd W a r where (Z the distance between the conductors and A is the wave length of the oscillatory current.

' Reterring' to Fig. 6 we have indicated the an'rent l in the antenna conductor A, and the current L, in the: antenna conductor B by vectors. Yi hcn the phase angle between the two currents is adjusted to equal,

fi'iT energy transn'iitten in the plane of conductors. i i and B. will be concentrated in one direction but stuistautially neutralized in the {l ction. 5 Theoretically the complete ,ristic of such a system will be sub- .1 fil3i1l2llly a cardioid.

, In practice it has been ditlicult to provide means whiolrwill give the correct phase anfor unidirec'ional characteristics, where both antenna conductors are supplied with energy from asingle source. However the system shown in l ig. l atlords a practical solution. of this problem.

.lteterring to Fig. 7, it will be noted that conductor 16 is tapped onto conductor 13 at a point to one side of the center, and that it is connected at lower end to condenser plate 18, whichin practice is not .iymnietrically located bctwcenplatcs 17. This asymmetrical arrangement is necessary. as other wise there would be no diti'erence of potential at the ends of conductor l6, and no current would flow therein. To further increase the current in conductor 16, only one side of the loop has been shown connected to the high potential side of the oscillator output, while the other side of the loop is coupled thereto y no of its distributed capacitance.

cei n control of the current distribution nay be had by shitting balancing}; electrode 1.8.;

menses;

We ha-Vefound. th'atrwitlrproper phasere:

lationships existing between currentsl I i-I 1 and 1 WVe have-:foundiin practicerithatc,

and 1 we can cause the system to have substantially unidirectioiialieffects. to the vector diagramof Fig. 8, it has been found thatvwith a proper phaseangle between currents I 1 and I .andwitlnproper proper? tionality :between the magnitudes of these.

cu-rrents,-: the effective. phase angle, between I alent to that of a current flowing 1n an imagt;

nary conductor Bi :which w is substantially equal to 1 but out :of phase .by an :amount equal to e ari Y l/Vit'h thesystem in this condition, transmissionis substantially unidirectional and the characteristic approximates a cardlold.

upon a certain wave length-.The best wave mined experimentally. However as explained above weprefer to utilize a conductor iforthe loop which isslightly lessithan one-quarter wave lengtlr'in circumference.

The distance between conductors 11 and 12 is"-alsol -preferablyequal. to about from 1/10th to 1/15th of the wave lengtlrem: ployed. Shiftingoflthe electrode 18 of the balancing device may be resorted to for securing the desirednonsymmetricaL current distribution. The magnitude of current I may lie-controlled both by shifting electrode 18. and by varying the capacitance 19.

l/Ve have :found that :the system will open ate toi secure directionalcharacteristics for variouspositions of c'onductor 16 relative to conductors 11 and 12. I We prefer however to locate conductor 16-130 one side of the center of the loop as shown, since this arrangement renders the system less critical to adjustments Thismay be explained by the fact that the imaginary conductor B haspropor-- tionally less distance to shi'ftin response to a change in the relative values ofcurrents- I and I tha-n would be thecase if conductors l6 and-12were plac-ed farther'apart.

Referring to F rguQ. we have shown curvesdrawn on polar coordinates which illustrate the characteristics'of the systeni with differ ent adjustments. Thepolar axis 1 'co-rre snonds *to' the pla'neof conductors-11 and 12.

' Curve 2shows the characteristic of the sys- Referring J timum conditions of operationarz. Currier-3 i c lustrates 1 how the. ChHJIZI'CtQIZlStlCSCZIHEIY-T be at; t varied i by: an improper V adjustment of genre-a are, enabled, in our system-:to change: the-:d

In vpractice it has-been found that a loop 'ofa given size :will operate most effectively capacitance 19, and the balancing electrode.

'ineFig. 10 is similar to 'thei-modificationsterm: vfor proper adjustmentszoiiirthesntirrentstzz approximates a cardioid andz representstop -iis I rents Land I This curveisino longera cardioid, but a the; majzority of; the-i energy zisn stillibeing radiated inrone :clirection. 1 Itis interesting .to note howeverxthat. the$dlf 3+1=- tion ,of maximumrradi ationis shifted z-tO ,line: 4 which isat an anglevto therpolaraaxissl.i. Thus by adjustingthecurrents l2 and" 13,1,W

rectional characteristics-and the direotim-of maximum radiation without physically; turns, 4

ins; the antenna structure.-

The system shown in Fig. 2 is-essentially i is adjusted by means of a single :yariablel'caw pacitance 32;,and this capacitance alsoserves to tune the loop to the desiredwavelength- One side of the loop is still directly connectedw to the high potential. point or to the plate of the oscillator 1.3 as sh6wn,.while capacitance 19 has been shown as connected to the low potential side of the inductance 22. The theoretical operation .of the system isxsub-Z:

lengthfifor :a particular loop --maybe def/61 :5; stantially the same as thatyofFighlj In'the system ofFigL 3 one; side, of'i'the 18 have been connected to thexground 335 In this case only one conductor 34' need be pro:- vided between one side of the loopxand {the oscillation generator 13,'this conductor being connected to the high potentialsideoftuned inductance. 22. This oscillator also employs A a blocking condenser 36 inserted between the" plate of relay 21 and the inductance 22:

The modification. of the invention 'shown;

previously described except "that-*we have shown a current transmissionliiie for transamitting high frequency energy from a re=v .mote oscillator to the antenna structure; and permit rotationof the antennamIn this case? we have shown the high potential side of the.

this transmission line .haslbeenumodified i301:

transmission line, or oscillator,connected-to;

that side of the loop which is nearestto the intermediate conductor 16, rather tha'nsthe other side as in the preceding forms. de-q scribed. Thus, the oscillator hasabeen indi-T catcd diagrammatically at 36fand supplies an. oscillatory circuit represented by a tuned inductance 37. Tapped upon inductance 37' are the transmission lines 38 which are prefer; ably, arranged inparallel.relationship As we propose to permit rotationof the-loop relative to the oscillator we preferably pro-; vide a pairotcond-u'ctors 39 i nthe form-of" thesaine asthat of Fig.v lfllnthis'casehow z e ever-the distribution of current=in the loopi are for efiiclent transmission of high frequency rings which are rotatable together with the loop structure, and which have connections to-the transmission lines 38 as my means of brushes 40. Inductance ll is connected across rings 39 and has a high potential terminal connected to one side of the antenna loop as by means of conductor 42. Conductor 42 preferably connects to that side of the loop formed by conductor 12, while the other side of the loop is coupled by its distributed capacitance represented by the capacitance 43.

In the system of Fig. 10, assuming an upward flow of current in conductor 12, current'flow in conductor 16 will be in an op- ;posite direction or downwardly, while the current flow in conductor 11 will likewise be downward. Therefore in order to secure the desired phase relationship to effect unidirectional transmission, the current I flowing in conductor 12 must be greater than current 1 in conductor' ll. The vector diagram for currents in conductors 11, 12 and 16, is shown in Fig. 11. Thus, as there shown, the current I is greater than current I while current I5 has a pl ase relationship with respect to current I such as to secure the correct phase angle by adjustment of variable capacitance 19. The direction of maximum radiation with this system has been indicated by the arrow.

The conductor rings 39 make up part of the electrical transmission line between inductances 37 and 41. It is of course nee-e sary energy, that the surge impedance of the line he made equal to the antenna impedance as measured across inductance 41, thus securing the effect of a line of infinite length.

It is obvious that our system may be used for both transmission and reception of radio signals and it is to be understood that by.

signaling circuit, we have reference to both Ecircuits for generation and reception of radio energy. However the system operates particularly well when transmitting signals upon short wave lengths.

M Ve claim 1. In an antenna system comprising a plu rality of parallel conductors lying in a common plane, the method of securing a unidirectional effect at any wave length which eomprises so ad]ust1ng the nnpedances of imaginary conductor spaced from said other more than two conductors spaced less than one-quarter wave lengthapart which comprises so adjusting the reactances of said conductors as to produce the effect of two spaced conductors carrying currents differing in phase by an angle equal to where (Z is the distance between them and is different from the actual distance between any of the real conductors, and a is the wave length of the current.

3., The method of securing unidirectional effects from a radio antenna employing a plurality of spaced conductors for effecting an interchange of energy with an absorbing medium, comprising effecting energization of one conductor with oscillatory current of a definite Wave length, and producing the effect of an imaginary conductor supplied with oscillatory current of the same wave length but out of phase with the current of the first conductor by an angle substantially equal to Ticwhere cl is the distance between the real and imaginary conductors and a is the wave length of the oscillatory current, said last mentioned effect being produced by supplying oscillatory currents of different phases to said additional real conductors.

4;. A radio transmitting system comprising a source of oscillatory energy, a plurality of radiating conductors all supplied with energy from said source and spaced apart a distance which is less than one fourth the wave length of the oscillations produced by the source, means for effecting a transfer of energy from said source to said conductors, and means for effecting a phase displacement of the currents in certain of said conductors for effecting substantially unidirectional transmission.

5. In a radio system, a source of oscillatory energy, an antenna conductor supplied with current from said source, another antenna conductor spaced from the first conductor and supplied with current from the same source, and means including a third antenna conductor connected in parallel with said other conductors for effecting substantially unidirectional characteristics for the system.

6. A directive radio system comprising a conductive loop with a signaling system coupled thereto and a conductor connected effectively in shunt across points of unequal potential in said loop, one end of said conductor being associated with said conductive loop through a reactance element.

7. A radio system comprising a tuned conductive loop, means for effecting non-symmetrical distribution of current in the loop, comprising a conductor connected in parallel across a portion of the loop, and means including a reactance for effecting a flow of current thru said conductor which is out of phase with current in the other parts of the loop, whereby the directional characteristics of the loop are affected. v

8. A directive antenna comprising at least three parallel conductors spaced less than one-quarter wave length apart and means for shifting the phase angle of some of said conductors with respect to others whereby there is produced the effect of two parallel conductors carrying currents differing by a distance between the effective conductors and )t is the wave length of the current. Y

9. A directive antenna comprising three parallel conductors spaced apart less than one quarter wave length of the exciting energy and connected together at one end, a transmission lineconnect-ed to the free ends of two of the conductors, and a Variable capacity coupling between the free end of the third conductor and the two sides of said transmission line.

phase angle equal to 1r i where d is the 10. A directive antenna as defined in claim 8, further characterized in this, that a variable condenser is inserted in series in said third conductor.

In testimony whereof we have hereunto set our hands.

FREDERICK A. KOLSTER. GEOFFREY G. KRUESI. 

